I received the following comment from Daniel L. Pohnert, professional engineer, with Fred Wilson & Associates Inc. in Jacksonville, FL:
"In your column in the June 1998 issue of Cabling Installation & Maintenance [see page 12], you mentioned that coaxial cable for cable TV is not required to be protected, according to the National Electrical Code (nec). Article 820 covers Community Antenna Television (catv), an early term for cable when remote communities would mount tall antennas to receive TV signals from distant cities. Per article 820-33, the outer conductor of the coaxial cable must be grounded. This ground shunts any charge built up on the outer conductor. This ground also acts as a de facto lightning arrestor for the inner conductor, since any high- voltage surge (3000 volts or higher) would puncture the insulation and drain through the ground connection. The let-through energy may still be enough to damage a TV or vcr.
"But it is correct that no surge arrestor device (primary protector) similar to that required by the nec, Article 800, for other communications circuits is required for cable TV."
I have since learned that while the nec does not require a primary pro- tector on cable-TV coaxial cable, some local jurisdictions do. Contact the authority having jurisdiction (ahj) for a determination in your work area.
